6x2 - Wire in the Blood

Another victim disappears and a severed finger is sent to constable Chris Collins in an envelope, suggesting that the killer is into playing cat and mouse games with him. Chris, a new young constable whose attitude Alex dislikes, then disappears and is abducted by the murderer who strips him and strings him up. Tony realizes that the killer is the sort of person that anybody would trust - such as a doctor - as he races to save Chris's life.